Aprea Therapeutics Announces Early Clinical Proof-Of-Concept in the Ongoing ACESOT-1051 Dose-Escalation Trial Evaluating WEE1 Inhibitor APR-1051, Including Partial Response Observed on First Scan

Rhea-AI Summary

Aprea Therapeutics (NASDAQ: APRE) reported early clinical proof-of-concept for single-agent WEE1 inhibitor APR-1051 in the Phase 1 ACESOT-1051 dose-escalation trial on Jan 29, 2026. An unconfirmed partial response was observed at the 150 mg dose with ~50% target lesion reduction and CA-125 fall from 732 to 70 U/mL.

Multiple patients showed stable disease and tumor reductions across 70 mg, 100 mg and 150 mg cohorts; 220 mg cohort is enrolling and dose escalation will continue to define the RP2D.

Positive

• Unconfirmed partial response at 150 mg with 50% tumor reduction
• CA-125 tumor marker fell from 732 to 70 U/mL in responder
• Durable on-treatment duration: patient on therapy >210 days
• Dose-response trend across 70 mg, 100 mg, 150 mg cohorts
• Enrollment progressing into 220 mg cohort

Negative

• Partial response is unconfirmed pending subsequent scans
• Early-phase data from dose escalation; RP2D not yet established
• Limited sample sizes per cohort limit statistical confidence

News Market Reaction – APRE

-22.78% 309.6x vol

93 alerts

-22.78% News Effect

+86.4% Peak Tracked

-30.8% Trough Tracked

-$3M Valuation Impact

$10M Market Cap

309.6x Rel. Volume

On the day this news was published, APRE declined 22.78%, reflecting a significant negative market reaction. Argus tracked a peak move of +86.4% during that session. Argus tracked a trough of -30.8% from its starting point during tracking. Our momentum scanner triggered 93 alerts that day, indicating high trading interest and price volatility. This price movement removed approximately $3M from the company's valuation, bringing the market cap to $10M at that time. Trading volume was exceptionally heavy at 309.6x the daily average, suggesting significant selling pressure.

Data tracked by StockTitan Argus on the day of publication.

Key Figures

Tumor reduction: 50% reduction in target lesion CA-125 decrease: >90% decrease in CA-125 CA-125 levels: 732 to 70 U/mL +5 more

8 metrics

Tumor reduction 50% reduction in target lesion Endometrial cancer patient at 150 mg dose, first scan

CA-125 decrease >90% decrease in CA-125 Endometrial cancer patient showing biomarker response

CA-125 levels 732 to 70 U/mL Tumor marker change in uterine serous carcinoma patient

Dose level 150 mg APR-1051 dose where unconfirmed partial response observed

Next cohort dose 220 mg Current enrolling dose cohort in ACESOT-1051

Tumor reduction 5% reduction HPV-positive HNSCC patient at 70 mg dose

Tumor reduction 15% reduction FBXW7-mutated colon cancer patient at 100 mg dose

Time on therapy Over 210 days Colon cancer patient at 100 mg approaching eighth treatment cycle

Market Reality Check

Price: $0.9167 Vol: Volume 86,984 is at 1.09x...

normal vol

$0.9167 Last Close

Volume Volume 86,984 is at 1.09x the 20-day average of 79,951 shares. normal

Technical Price $0.7641 is trading below the 200-day MA ($1.46) and far under the $4.65 52-week high, hovering just above the $0.73 52-week low.

Peers on Argus

Momentum scanner flagged APRE separately (target_direction: up) with no peers in...

Momentum scanner flagged APRE separately (target_direction: up) with no peers in momentum. Among high-affinity biotech peers, several traded lower (e.g., CYCCP -5.61%, INAB -6.22%, RNAZ -2.46%) while KPRX was modestly higher (+0.47%), suggesting APRE’s setup was more stock-specific than a broad sector move.

Historical Context

5 past events · Latest: Dec 18 (Positive)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
Dec 18	Shareholder letter	Positive	-0.0%	CEO letter outlining 2025 clinical progress and 2026 development plans.
Dec 09	Private placement	Negative	-10.8%	At-the-market private placement raising <b>$3.1M</b> with new warrants issued.
Nov 12	Q3 earnings	Negative	-4.5%	Q3 2025 loss, limited cash runway and clinical updates on APR-1051 and ATRN-119.
Oct 24	Clinical update	Positive	-7.9%	Early ACESOT-1051 data showing stable disease signals without dose-limiting toxicities.
Oct 15	Clinical trial	Neutral	-1.3%	RP2D set for ATRN-119 and shift toward combination strategies; APR-1051 enrolling.

Pattern Detected

Recent APRE news, including clinical and financing updates, often coincided with flat-to-negative next-day moves, even on generally constructive clinical disclosures.

Recent Company History

Over the last few months, Aprea highlighted steady progress for WEE1 inhibitor APR-1051 in ACESOT-1051, advancing doses up to 220 mg and reporting early disease-stabilization and tumor reduction signals. In parallel, ATR inhibitor ATRN-119 reached an RP2D of 1,100 mg QD, with monotherapy enrollment paused to prioritize combinations. The company also completed a $3.1M private placement and reported Q3 2025 results with ongoing net losses. Despite these constructive pipeline milestones, shares often traded down or flat after announcements, setting the backdrop for today’s more detailed proof-of-concept data.

Market Pulse Summary

The stock dropped -22.8% in the session following this news. A negative reaction despite positive ea...

Analysis

The stock dropped -22.8% in the session following this news. A negative reaction despite positive early efficacy data fits a pattern where APRE’s constructive news, such as prior ACESOT-1051 updates, was followed by weak trading. The stock sat well below its $4.65 52‑week high and just above its $0.73 low pre-announcement, with a market cap near $5.8M, so dilution history and listing-risk disclosures may have kept sentiment cautious even as clinical signals improved.

Key Terms

wee1 inhibitor, recist v1.1, ca-125, uterine serous carcinoma, +4 more

8 terms

wee1 inhibitor medical

"dose-escalation Trial Evaluating WEE1 Inhibitor APR-1051, Including"

A Wee1 inhibitor is a drug that blocks the Wee1 protein, which normally acts like a safety brake that pauses damaged cells before they divide. By removing that brake, cancer cells with DNA damage are forced into division and often die, making the approach useful for targeting tumors. Investors track Wee1 inhibitors because their clinical trial success, safety profile and use with other therapies can greatly affect a biotechnology company's value.

recist v1.1 medical

"50% reduction in target lesion size per RECIST v1.1 criteria, along"

RECIST v1.1 is a standardized set of rules used in cancer trials to measure how solid tumors change over time, defining when tumors shrink, grow, or stay the same based on imaging scans. Investors care because these consistent measurements determine key trial results and regulatory decisions—like whether a drug is seen as effective—so RECIST-based outcomes directly affect a therapy’s approval prospects, market potential, and company valuation.

ca-125 medical

"greater than 90% decrease in CA-125 observed in endometrial cancer patient"

CA-125 is a protein measured in the blood that often rises when certain cancers, especially ovarian cancer, are present or returning; doctors use it like a dashboard warning light to monitor disease activity, treatment response, and possible relapse rather than as a definitive diagnostic test. For investors, changes in CA-125 levels can affect clinical trial outcomes, regulatory decisions, and demand for diagnostic tests or therapies, so it can influence a company’s clinical progress and market prospects.

uterine serous carcinoma medical

"patient with PPP2R1A-mutated uterine serous carcinoma, a form"

A rare, aggressive form of uterine cancer that starts in the lining of the womb and behaves more like a fast-spreading tumor than the more common, slower-growing types. It matters to investors because its severity and distinctive biology drive demand for specialized treatments, diagnostics, and clinical trials, which can influence the commercial potential and regulatory value of new drugs or tests—similar to a niche but high-impact market within cancer care.

hpv-positive medical

"increase enrollment of HPV-positive patients in the ongoing trial."

hpv-positive indicates that human papillomavirus (HPV) genetic material or infection has been detected in a biological sample, often a tumor; it's like finding a fingerprint that points to a specific cause. For investors, that designation matters because HPV-positive status can change expected treatment pathways, clinical trial eligibility, regulatory review, and market demand for diagnostics or therapies, which in turn affects the commercial outlook for related medical products.

ppp2r1a medical

"PPP2R1A-mutated uterine serous carcinoma, a form of endometrial"

PPP2R1A is a human gene that makes a key part of a molecular “brake” inside cells that helps control growth and repair by turning off certain biochemical signals. Mutations or abnormal activity in this gene are linked to some cancers and other diseases, so it matters to investors because it can be a target for drugs, affect the value of diagnostics or therapies, and influence the commercial outlook of biomedical projects.

fBXW7 medical

"a patient with FBXW7-mutated colon cancer treated at the 100 mg dose."

FBXW7 is a human gene that makes a protein acting like a cellular quality-control inspector, tagging worn-out or excess proteins for removal so cells behave normally. Changes or loss of this inspector can let damaged cells grow unchecked, which is often linked to cancer, so knowing a tumor’s FBXW7 status can affect the potential value of diagnostic tests, targeted treatments, and related investment risk or opportunity in biotech pipelines.

recommended phase 2 dose medical

"dose escalation continuing into higher dose cohorts to establish the recommended Phase 2 dose"

Recommended phase 2 dose is the specific drug amount chosen after initial human studies to use in mid-stage clinical trials that assess whether the treatment works and remains reasonably safe in patients. Investors pay attention because that dose determines how convincing the upcoming trial results are likely to be, influences the size, cost and duration of further studies, and affects the chance of regulatory approval and commercial success—much like picking the right test speed to judge a new car's performance without risking damage.

AI-generated analysis. Not financial advice.

• Approximately 50% reduction in target lesion and greater than 90% decrease in CA-125 observed in endometrial cancer patient
• The unconfirmed partial response (uPR) that was observed in the first scan has been achieved at the 150 mg dose, with 220 mg cohort currently enrolling in the ACESOT-1051
• Potential dose-response trend observed with increasing single-agent activity across the 70 mg, 100 mg, and 150 mg cohorts
• Data provide early clinical proof-of-concept for single-agent APR-1051 in patients with advanced solid tumors

DOYLESTOWN, Pa., Jan. 29, 2026 (GLOBE NEWSWIRE) -- Aprea Therapeutics, Inc. (Nasdaq: APRE) (“Aprea” or the “Company”), a clinical-stage biopharmaceutical company developing innovative therapies that exploit cancer-specific vulnerabilities while minimizing damage to healthy cells, today announced the first unconfirmed partial response (uPR) observed in a patient enrolled in its ongoing Phase 1 ACESOT-1051 dose-escalation study (A Multi-Center Evaluation of WEE1 Inhibitor APR-1051 in Patients with Advanced Solid Tumors).

This early clinical activity was observed in a patient with PPP2R1A-mutated uterine serous carcinoma, a form of endometrial cancer, treated at the 150 mg dose level of APR-1051, with dose escalation continuing into higher dose cohorts to establish the recommended Phase 2 dose (RP2D). At the protocol-defined 8-week imaging assessment, the patient achieved a 50% reduction in target lesion size per RECIST v1.1 criteria, along with a marked reduction in cancer antigen 125 (CA-125) levels, from 732 to 70 U/mL, a well-recognized tumor marker in endometrial cancer.

In earlier cohorts of ACESOT-1051 study, multiple patients achieved stable disease with reductions in tumor burden, including a 5% reduction at the 70 mg dose in a patient with HPV-positive head and neck squamous cell carcinoma (HNSCC) and a 15% reduction in a patient with FBXW7-mutated colon cancer treated at the 100 mg dose. This patient has remained on therapy for over 210 days and is approaching their eighth treatment cycle. In addition, a second patient treated at the 150 mg dose level achieved stable disease at the first follow-up imaging assessment.

Collectively, these findings suggest that APR-1051 may have therapeutic potential across a range of solid tumors. Enrollment in the 220 mg dose level cohort of the study is currently underway, and the company intends to increase enrollment of HPV-positive patients in the ongoing trial.

“These early single-agent data demonstrate that APR-1051 has clinical activity as a single agent,” said Anthony Tolcher, MD, FRCPC, Principal Investigator at Next Oncology. “The observation of a partial response on the first scan, together with a decrease in tumor marker at this dose level, supports continued clinical evaluation of APR-1051.”

Oren Gilad, PhD, Chief Executive Officer of Aprea Therapeutics, added, “These preliminary results provide early proof-of-concept for single-agent activity of APR-1051 and support our strategy of targeting cancers with specific genomic alterations, including HPV-positive disease and PPP2R1A, FBXW7, CCNE1, TP53 and KRAS mutations. The potential dose-response trend and favorable safety profile observed in the ongoing dose-escalation study reinforce our confidence in the potential of APR-1051 as a differentiated WEE1 inhibitor for patients with advanced solid tumors. We look forward to providing additional updates in the first half of 2026 and completing dose escalation later in the year.”

About the ACESOT-1051 Trial

ACESOT-1051 is a first-in-human, open-label Phase 1 study evaluating the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of single-agent APR-1051 in patients with advanced solid tumors harboring cancer-associated genetic alterations. The dose-escalation portion of the study is expected to enroll up to 50 patients across nine planned dose cohorts, ranging from10 mg to 300 mg administered once daily. APR-1051 is administered orally once daily in continuous 28-day cycles. To date, enrollment has evaluated doses up to 150 mg, with the 220 mg cohort currently enrolling. For more information, refer to ClinicalTrials.gov ID NCT06260514.

About Aprea
Aprea is pioneering a new approach to treat cancer by exploiting vulnerabilities associated with cancer cell mutations. This approach was developed to kill tumors but to minimize the effect on normal, healthy cells, decreasing the risk of toxicity that is frequently associated with chemotherapy and other treatments. Aprea’s technology has potential applications across multiple cancer types, enabling it to target a range of tumors, including ovarian, endometrial, colorectal, prostate, and breast cancers.

The company’s lead programs are APR-1051, an oral, small-molecule inhibitor of WEE1 kinase, and ATRN-119, a small molecule ATR inhibitor, both in clinical development for solid tumor indications. For more information, please visit the company website at www.aprea.com.

Forward-Looking Statement

Certain information contained in this press release includes “forward-looking statements”, within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended related to our study analyses, clinical trials, regulatory submissions, and projected cash position. We may, in some cases use terms such as “future,” “predicts,” “believes,” “potential,” “continue,” “anticipates,” “estimates,” “expects,” “plans,” “intends,” “targeting,” “confidence,” “may,” “could,” “might,” “likely,” “will,” “should” or other words that convey uncertainty of the future events or outcomes to identify these forward-looking statements. Our forward-looking statements are based on current beliefs and expectations of our management team and on information currently available to management that involve risks, potential changes in circumstances, assumptions, and uncertainties. All statements contained in this press release other than statements of historical fact are forward-looking statements, including statements regarding our ability to develop, commercialize, and achieve market acceptance of our current and planned products and services, our research and development efforts, including timing considerations and other matters regarding our business strategies, use of capital, results of operations and financial position, and plans and objectives for future operations. Any or all of the forward-looking statements may turn out to be wrong or be affected by inaccurate assumptions we might make or by known or unknown risks and uncertainties. These forward-looking statements are subject to risks and uncertainties including, without limitation, risks related to the success, timing, and cost of our ongoing clinical trials and anticipated clinical trials for our current product candidates, including statements regarding the timing of initiation, pace of enrollment and completion of the trials (including our ability to fully fund our disclosed clinical trials, which assumes no material changes to our currently projected expenses), futility analyses, presentations at conferences and data reported in an abstract, and receipt of interim or preliminary results (including, without limitation, any preclinical results or data), which are not necessarily indicative of the final results of our ongoing clinical trials, our understanding of product candidates mechanisms of action and interpretation of preclinical and early clinical results from its clinical development programs, and our ability to predict clinical outcomes based on such preclinical and early clinical results, our ability to continue as a going concern, and the other risks, uncertainties, and other factors described under “Risk Factors,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in the documents we file with the U.S. Securities and Exchange Commission. For all these reasons, actual results and developments could be materially different from those expressed in or implied by our forward-looking statements. You are cautioned not to place undue reliance on these forward-looking statements, which are made only as of the date of this press release. We undertake no obligation to update such forward-looking statements for any reason, except as required by law.

Investor Contact:

Mike Moyer
LifeSci Advisors
mmoyer@lifesciadvisors.com

FAQ

What did Aprea (APRE) report about APR-1051 in the ACESOT-1051 trial on Jan 29, 2026?

Aprea reported an unconfirmed partial response at the 150 mg dose with ~50% target lesion reduction and CA-125 decline from 732 to 70 U/mL. According to the company, additional patients showed stable disease across 70 mg, 100 mg and 150 mg cohorts and 220 mg enrollment is underway.

How significant is the partial response observed for APRE's APR-1051 at 150 mg?

The response is an early signal: a ~50% RECIST reduction plus CA-125 fall to 70 U/mL at 8 weeks. According to the company, this is an unconfirmed partial response from a PPP2R1A-mutated uterine serous carcinoma patient and requires follow-up imaging to confirm.

What does the APR-1051 dose-response trend mean for APRE investors?

A potential dose-response trend suggests increasing single-agent activity from 70 mg to 150 mg cohorts, with further assessment at 220 mg. According to the company, this pattern supports continued dose escalation to establish the recommended Phase 2 dose.

Which tumor types showed activity with APR-1051 in Aprea's ACESOT-1051 study?

Observed activity included PPP2R1A-mutated uterine serous carcinoma, HPV-positive HNSCC and FBXW7-mutated colon cancer with tumor reductions and stable disease. According to the company, responses span multiple solid tumors, prompting targeted enrollment increases for HPV-positive patients.

What are the near-term clinical milestones for APRE and APR-1051 after this Jan 29, 2026 update?

Near-term milestones include completing dose escalation, defining an RP2D, and providing additional study updates in the first half of 2026. According to the company, enrollment is ongoing at 220 mg and the firm expects to complete escalation later in 2026.